AN EMPIRICAL-MODEL FOR THE LACTATION CURVE OF WHITE BRITISH DAIRY GOATS

A survey of dairy herds was undertaken to establish an empirical model for the goat lactation curve. The adopted model will be used to predict milk output from commercially kept dairy goats. It is also desirable for the model parameters to be easily interpretable in terms of shape and scale of the curve. Records for 152 goat lactations from a Research Institute and 255 lactations in five commercial herds were analysed. Three groups of equations were fitted to individual goats from the Research Institute herd. The most suitable model was selected after study of residuals and consideration of the model parameters. The adopted model was of the form: y = A exp(B(1 + n'/2)n' + Cn'2 - 1.01/n) where y = daily yield in kg; n = day of lactation (post parturition); and n' = (n - 150)/100. This model was then validated with lactation data from the five commercial herds. There was no evidence to reject the adopted model.